New Estimates on Health Coverage Are Accurate but Outdated

The federal government released some very reliable estimates of how many people had health insurance in the first three months of 2014. But the data won’t tell us much about how many people got insurance through the Affordable Care Act.

Most people who got coverage through the law signed up very late. The combination of the buggy Healthcare.gov site and people’s natural tendency to procrastinate meant that enrollment in the new health care program surged at the end of March and the beginning of April, after the government finished doing most of the interviews for its survey.

After people signed up, it took a little time for their coverage to kick in. That means that only a fraction of people insured through the health care law could answer “yes” early this year when government researchers asked them whether they had health insurance.

The numbers, which show a 1.3 percentage point decline in the number of Americans who lacked health insurance in the first three months of this year, were released early Tuesday as the latest installment in the National Health Interview Survey. The questions are designed by the Centers for Disease Control and Prevention, which has been measuring insurance rates for more than 50 years. The methods of their survey and their long data set make the estimates highly reliable and useful for researchers. In time, government estimates will come to capture the full enrollment period. But for now, the survey includes only interviews from the first three months of the year.

Health insurance is a notoriously difficult thing to poll people about because most people find health insurance hard to understand. The government surveys tend to be well designed and careful, which is why most social scientists trust them more than private surveys when it comes to measuring people’s access to health care.

“Insurance status seems really straightforward, but it can be very confusing for people,” said Mollyann Brodie, the executive director of public opinion and survey research at the Kaiser Family Foundation and president-elect of the American Association of Public Opinion Research. The federal survey includes more questions and follow-up than the typical private telephone or Internet survey.

But the downside to the careful government approach is that it’s slow. Traditional polling operations, like Gallup, have been collecting data and publishing results much more quickly.

There are reasons Gallup data may not be as complete as C.D.C. figures, but, for now, it’s much more useful because it’s current. The latest installment, which included polling from the end of May, showed that the percentage of American adults without health insurance had plummeted from 18 percent in mid-2013 to 13.4 percent. (Other recent surveys show a decline similar to Gallup’s.)

The C.D.C. data, by contrast, was gathered early this year, meaning, on average, it tells us what the uninsurance rate looked like in February. It may be accurate, but it doesn’t tell us much about the Affordable Care Act.